Although Prophyromonas gingivalis has been implicated as a potential periodontopathic organism, the identification of its virulence factors has been equivocal. Therefore, this application proposes to utilize molecular genetic approaches in conjunction with both in vitro and animal model systems to assess the contribution of several P. gingivalis gene products as potential virulence factors. The genes coding for collagenase, superoxide dismutase, trypsinlike protease, a hemagglutinin, and the collagen-binding adhesin will be examined in this regard. The first four genes have recently been isolated in this laboratory on a single 5.9 kb DNA fragment from strain 53977. The later gene will be isolated from a lambda clone bank utilizing an immunoblot detection system. The genes will be characterized and sequenced (the collagenase and superoxide dismutase genes have been sequenced) and this information utilized to examine the regulation of expression of each gene. Since hemin affects the expression of several of these genes, it will be of interest to,determine the molecular basis for such regulation. Mutants of P. gingivalis defective in each gene will be isolated either by transformation following electroporation or utilizing chemical mutagenesis followed by enrichment techniques. These mutants will be tested in the mouse virulence system to assess the role of each gene in pathogenicity, as well as with in vitro model systems. This approach should aid in identifying periodontopathic virulence factors whose neutralization could reduce P. gingivalis pathogenicity.